Recently, many image forming apparatuses such as copiers, printers, and facsimiles can form color images, and such digital color printing apparatuses are rapidly becoming widespread. The digital color printing apparatuses are replacing digital monochrome printing machines currently used in offices.
Such an image forming apparatus can easily print a color document created using so-called presentation software, color image data taken with digital cameras, etc., in an office.
However, printing must be also performed for text data or form outputs written only in black and white and documents previously filed electronically as monochrome data, and such documents are also printed by the digital printing apparatus.
When the digital printing apparatus prints and outputs black and white pages, a print mode must be switched from a color mode to a black-and-white mode (monochrome mode) from a viewpoint of print cost and apparatus life. This switching is performed for each page by judging first an attribute of each page of the document (i.e., whether a color page or a black-and-white page) in an image processing apparatus that supplies image data to an image forming apparatus before printing, and by transmitting the judged attribute and the image data corresponding to the document to the color printing apparatus. Some color printing apparatuses include such a judging function of the image processing apparatus.
Conventional image processing apparatuses that switch the color mode and the monochrome mode to print include a color/monochrome distributed printing system that references at least one of either text data or image data included in print data to judge into which the print data is classified, color information or monochrome information (see Japanese Laid-Open Patent Publication No. 2004-070521).
In a conventionally proposed image processing apparatus, pixel data represented by four colors of CMYK respectively are converted into a uniform color space such as CIEXYZ and CIELAB spaces and it is judged to be a color image if the color difference after conversion is a certain value or more and to be a black-and-white image if the color difference is a certain value or less (see Japanese Laid-Open Patent Publication No. 2003-244452).
In a conventionally proposed image data creating apparatus, object data included in each band that is one of a plurality of partial images obtained by dividing an image are checked and it is judged that a band is color if the band includes color and that a band is monochrome data if the band does not include an object to be depicted in color (see Japanese Laid-Open Patent Publication No. 2002-044465).
In a conventionally proposed information processing apparatus, a print command received from a host apparatus such as a personal computer is analyzed and converted into predetermined intermediate data, all the pixels of RGB image data generated based on the converted intermediate data are judged (hereinafter, called “color/monochrome judgment”) that they are color or monochrome, and CMYK image data are generated based on the result of this judgment (see Japanese Laid-Open Patent Publication No. 2003-320715).
However, although a user can set the standard of color judgment in the conventional color/monochrome distributed printing system described in Japanese Laid-Open Patent Publication No. 2004-070521, the system is not designed to accurately perform the color/monochrome judgment.
Although the consumed image memory can be minimized in the conventional image processing apparatus described in Japanese Laid-Open Patent Publication No. 2003-244452, the apparatus also is not designed to accurately perform the color/monochrome judgment.
Although the overall speed for creating image data can be improved in the conventional image data creating apparatus described in Japanese Laid-Open Patent Publication No. 2002-044465, the apparatus also is not designed to accurately perform the color/monochrome judgment.
The conventional information processing apparatus described in Japanese Laid-Open Patent Publication No. 2003-320715 can accurately perform the color/monochrome judgment by performing the color/monochrome judgment for all the pixels of the image data generated from the print intermediate data. However, since the judgment is performed for all the pixels, a processing amount is increased and the processing cannot be performed rapidly. Since this conventional information processing apparatus generates a second image data based on the result of the color/monochrome judgment, an additional memory area is needed, and since a special process must be performed by a special circuit or software for generating the final image data, the processing cannot be performed rapidly.